I have peeled the tint off one window with a razor blade scraper and it left some kind of coating behind, not quite adhesive but kind of cloudy. My guess it used to be some kind of adhesive many decades of AZ sun ago.

I have not tried power tools (like with a 3M wheel) nor have I tried inorganics such as HCl. I haven't tried steel wool nor have I tried sandpaper. I have not tried heat, as from a torch or heat gun. As far as organics, I have not tried toluene or gasoline, diesel, kerosene or alcohol.